2-amino-7-(heterocyclomethyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-ones and pharmaceutical uses and compositions containing the same

ABSTRACT

Disclosed is a compound containing a 2-amino-7-(substituted methyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one wherein substituted methyl is --CH 2  --R wherein R is an optionally substituted heteroalicyclic group, a pharmaceutical composition containing the compound, and a method for the selective suppression of mammalian T-cell function without diminished effect on humoral immunity which involves administering the composition to a mammal.

The present invention relates to derivatives of 2-amino-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one.

Purine nucleoside phosphorylase (PNP) catalyzes the phosphorolysis of purine nucleosides in a reversible reaction.

Individuals who are deficient in PNP exhibit impaired T-cell development, resulting in lowered cell-mediated immunity, but normal B-cell development, resulting in normal humoral immunity. Accordingly, specific inhibitors of PNP that selectively inhibit T-cell development without damaging humoral immunity could be potentially effective against disorders in which activated T-cells are pathogenic.

Accordingly, the present invention is a PNP inhibitor that is a derivative of 2-amino-7-methyl-3H,5H-pyrrolo[3,2-d]-pyrimidin-4-one.

In a first aspect of the invention there is provided a compound 2-amino-7-(substituted methyl)-3H,5H-pyrrolo[3,2-d]-pyrimidin-4-one (I) wherein substituted methyl is

    --CH.sub.2 --R.

The R group is an optionally substituted heteroalicyclic group. Preferably, the heteroalicyclic group is a 5 or 6 membered saturated ring having oxygen, nitrogen, or sulfur as the heterocyclic atom. More preferably the heteroalicyclic group is 2- or 3-tetrahydrothienyl, 2-, 3-, or 4-piperidinyl, 2- or 3-tetrahydrofuranyl, 2-, or 3-pyrrolidinyl, or 2-, 3-, or 4-tetrahydropyranyl. In a preferred aspect, R is unsubstituted, e.g., the compound (I) is 2-amino-7-(2-piperidinylmethyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one (IB), 2-amino-7-(3-piperidinylmethyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one (IC), 2-amino-7-(4-piperidinylmethyl)-3H-,5H-pyrrolo[3,2-d]pyrimidin-4-one (ID), 2-amino-7-(2-tetrahydrofuranylmethyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one (IE), 2-amino-7-(3-tetrahydrofuranylmethyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one (IF), 2-amino-7-(2-tetrahydrothirnylmethyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one (IG), 2-amino-7-(3-tetrahydrothienylmethyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one (IH), 2-amino-7-(2-pyrrolidinylmethyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one (II), 2-amino-7-(3 -pyrrolidinylmethyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one (IJ), 2-amino-7-(2-tetrahydropyranylmethyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one (IL), 2-amino-7-(3-tetrahydropyranylmethyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one (IM), or 2-amino-7-(4-tetrahydropyranylmethyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one (IN). In an alternative preferred embodiment the R has one or two substituents selected from the group consisting of halogen, hydroxy, alkoxy, alkyl, or trifluoromethyl. As halogen is preferably mentioned chloro or fluoro. As alkoxy is preferably mentioned lower alkoxy, including methoxy, ethoxy, propoxy and butoxy. As alkyl is preferably mentioned lower alkyl, including methyl, ethyl, propyl and butyl.

In a second aspect of the invention there is provided a method for the selective suppression of mammalian T-cell function without diminished effect on humoral immunity which comprises administering to a mammal the compound (I), whereby said compound inhibits purine nucleoside phosphorylase and thereby T-cell formation.

In a further aspect of the present invention there is provided a pharmaceutical composition for the selective suppression of mammalian T-cell function without diminished effect on humoral immunity which comprises an effective amount of the compound (I) and a pharmaceutically acceptable diluent therefor.

The invention further relates to pharmaceutical compositions suitable for enteral, such as oral or rectal, transdermal and parenteral administration to mammals including man, which are useful to inhibit purine nucleoside phosphorylase activity and for the treatment of disorders responsive thereto, comprising an effective amount of a pharmacologically active compound of the invention, alone or in combination, with one or more pharmaceutically acceptable carriers.

Preferred pharmaceutical compositions are tablets and gelatin capsules comprising the active ingredient together with (a) diluents, e.g., lactose, dextrose, sucrose, mannitol, sorbitol, cellulose and/or glycine; (b) lubricants, e.g., silica, talcum, stearic acid, its magnesium or calcium salt and/or polyethyleneglycol; for tablets also (c) binders, e.g., magnesium aluminum silicate, starch paste, gelatin, tragacanth, methylcellulose, sodium carboxymethylcellulose and/or polyvinylpyrrolidone; if desired (d) disintegrants, e.g., starches, agar, alginic acid or its sodium salt, or effervescent mixtures; and/or (e) absorbents, colorants, flavors and sweeteners. Injectable compositions are preferably aqueous isotonic solutions or suspensions, and suppositories are advantageously prepared from fatty emulsions or suspensions. Said compositions may be sterilized and/or contain adjuvants, such as preserving, stabilizing, wetting or emulsifying agents, solution promoters, salts for regulating the osmotic pressure and/or buffers. In addition, they may also contain other therapeutically valuable substances. Said compositions are prepared according to conventional mixing, granulating or coating methods, respectively, and contain about 0.1 to 75%, preferably about 1 to 50%, of the active ingredient.

Suitable formulations for transdermal application include an effective amount of a compound of the invention with a carrier. Advantageous carriers include absorbable pharmacologically acceptable solvents to assist passage through the skin of the host. Characteristically, transdermal devices are in the form of a bandage comprising a backing member, a reservoir containing the compound optionally with carriers, optionally a rate controlling barrier to deliver the compound to the skin of the host at a controlled and predetermined rate over a prolonged period of time, and means to secure the device to the skin.

The present invention provides a method of inhibiting purine nucleoside phosphorylase activity in mammals and treating diseases and conditions responsive thereto, e.g., autoimmune disorders, rejection of transplantation, or psoriasis, which comprises administering to a mammal in need thereof an effective amount of a compound of the invention or of a pharmaceutical composition comprising a said compound in combination with one or more pharmaceutically acceptable carriers.

A further aspect of the invention relates to a method of inhibiting the phosphorolysis and metabolic breakdown of antiviral or antitumor purine nucleosides in mammals which comprises administering in conjunction therewith to a mammal in need thereof, either separately or in combination therewith, an effective purine nucleoside phosphorylase inhibiting amount of a compound of the invention or of a said compound in combination with one or more pharmaceutically acceptable carriers. More particularly, such relates to a method of inhibiting the phosphorolysis and metabolic breakdown of purine nucleosides known in the art, e.g., of 2'-deoxyguanosine, 2',3'-dideoxyinosine, 2',3'-dideoxyguanosine or 2',3'-dideoxyadenosine.

Furthermore, the invention thus relates to a method of potentiating the antiviral or antitumor effect of 2' or 3'-monodeoxypurine nucleosides or of 2',3'-dideoxypurine nucleosides in mammals which comprises administering in conjunction therewith to a mammal in need thereof, either separately or in combination with a said nucleoside, an effective purine nucleoside phosphorylase inhibiting amount of a compound of the invention preferably in combination with one or more pharmaceutically acceptable carriers. More particularly, such relates to a method of enhancing or potentiating the effect of 2',3'-dideoxypurine nucleosides known in the art, e.g., of 2',3'-dideoxyinosine, 2',3'-dideoxyguanosine or 2'-3'-dideoxyadenosine for the treatment of retrovirus infections, e.g., HIV-retrovirus infections (acquired immunodeficiency syndrome, AIDS). 2',3'-Dideoxypurine nucleosides are known in the art as inhibitors of HIV retrovirus infectivity and to be metabolically degraded by PNP, e.g., as described in Biochemical Pharmacology 22, 3797 (1987). Such are administered at a pharmaceutically acceptable dose which is effective in inhibiting HIV-retrovirus infections. Preferably the lowest possible effective dose is used.

The pharmaceutically acceptable effective dosage of active compound of the invention to be administered is dependent on the species of warm-blooded animal (mammal), the body weight, age and individual condition, and on the form of administration.

The pharmaceutical composition may be oral, parenteral, suppository or other form which delivers the compound (I) into the bloodstream of a mammal to be treated. An oral form has from about 1 to about 150 mg of the compound (I) for an adult (50 to 70 kg) which is mixed together with pharmaceutically acceptable diluents such as lactose. In a typical capsule, 25 mg of the compound (I) are mixed together with 192 mg lactose, 80 mg modified starch and 3 mg magnesium stearate. Injectable forms of the compound are also contemplated for administration.

The present invention is also useful with other therapeutic agents. A daily dosage for a human weighing 50 to 70 kg of 1-50 mg/kg inhibits metabolic destruction of certain anticancer agents such as beta-2'-deoxy-6-thioguanosine and antiviral agents such as 2',3'-dideoxyinosine, an anti-AIDS drug. These types of agents are known to be susceptible to cleavage. Upon cleavage, the agents lose effectiveness. The compounds of the present invention are capable of reducing such cleavage. This protection, therefore, enhances the efficacy of other chemotherapeutic agents.

One method of making the compound (I) of the present invention uses 3-substituted propionitriles as starting materials. Such starting materials can be obtained by a variety of methods that are well documented in the literature. The compound (I) is then prepared from the starting material by an adaptation of the synthetic methodology disclosed in M. I. Lim, R. S. Klein, and J. J. Fox, J. Oro. Chem., 44, 3826 (1979); M. I. Lim, R. S. Klein, and J. J. Fox, Tetrahedron Lett., 21, 1013 (1980); M. I. Lim and R. S. Klein, Tetrahedron Lett., 22, 25 (1981); M. I. Lim, W. Y. Ren, B. A. Otter, and R. S. Klein, J. Org. Chem., 48, 780 (1983).

In order to more fully describe the present invention the following non-limiting examples are provided. In the examples all parts and percentages are by weight unless indicated otherwise. Proportions of solvent mixtures used as chromatographic eluents are by volume.

EXAMPLE 1

3-(3-Pyridinyl)propionitrile is prepared in this example. A three-neck flask carrying a magnetic stir bar is fitted with a thermometer, pressure equalizing addition funnel, and a reflux condenser carrying an argon inlet. Freshly powdered potassium hydroxide (6.6 g, 0.1 mol) and anhydrous acetonitrile (150 ml) are charged into the flask and heated at reflux while 3-pyridinecarboxaldehyde (10.7 g, 0.1 mol) in anhydrous acetonitrile (50 ml) is added dropwise over a period of about five minutes and refluxing continued for about another three minutes. The resulting hot reaction mixture is poured into an ice/water mixture (100 g), and the resulting solution is extracted with CH₂ Cl₂ (3×100 ml), dried with Na₂ SO₄, and evaporated to give crude 3-(3-pyridinyl)acrylonitrile, which is purified by column chromatography over silica gel using CHCl₃ as the eluent; yield 3.3 g (25.6%).

Under an argon atmosphere, a stirred solution of the acrylonitrile (2.662 g, 0.02 mol) in 99% ethanol (100 ml) is treated with a drop of 4% aqueous sodium hydroxide followed by sodium borohydride (0.378 g, 0.01 mol). Additional sodium borohydride (0.378 g) is added twice more at four-hour intervals. The mixture is stirred at room temperature overnight, diluted with water, extracted with EtOAc and dried with Na₂ SO₄. The solvent is removed under reduced pressure and the crude product obtained is chromatographed over a column of silica using chloroform/methanol (40/1) as the eluent to give 2.2 g (84.6%) of the product as a colorless oil.

EXAMPLE 2

3-(3-Pyridinyl)propionitrile of Example 1 is further treated in the synthesis of the present invention. Under an atmosphere of dry N₂, a mixture of 3-(3-pyridinyl)propionitrile (0.661 g, 5.0 mmole), sodium hydride (0.240 g, 10.0 mmole), and ethyl formate (1.11 g, 15.0 mmole) in anhydrous tetrahydrofuran (20 ml) is stirred for 48 hours with protection from air and moisture. Volatile matter is evaporated, and a solution of the solid residue in 15 ml of cold water is adjusted at 0° C. to a pH of 6 with cold 6N HCl. The resulting oily mixture is extracted with CHCl₃ and the extract is washed with water, dried using Na₂ SO₄, and evaporated to give a dark oil, which is a mixture of 2-formyl-3-(3-pyridinyl)propionitrile and the nitrile starting material. This crude product is used in the next reaction without further purification.

EXAMPLE 3

Glycine methyl ester hydrochloride (0.942 g, 7.5 mmole) and anhydrous sodium acetate (0.615 g, 7.5 mmole) are added to a solution of the crude formyl compound (0.89 g) in MeOH/H₂ O (4:1, 50 ml). After 24 hours, the MeOH is evaporated in vacuo, and the mixture of water and oil is extracted with CHCl₃. The CHCl₃ layer is dried (Na₂ SO₄) and evaporated to give an amber oil which is applied to a silica gel column. Elution with CHCl₃ gave two major bands: (1) 3-(3-pyridinyl)propionitrile (used as starting material in the previous step), and (2) the desired enamine.

EXAMPLE 4

Under a nitrogen atmosphere, ethyl chloroformate (0.521 g, 4.8 mmole) is added dropwise to a solution of the enamine of Example 3 (0.513 g, 3.2 mmole) and DBN (1.37 g, 11.1 mmole) in dry CH₂ Cl₂ (15 ml) with external cooling in an ice bath. After stirring at 0° C. for one hour, the solution is allowed to a stand at room temperature overnight. After checking progress by TLC, additional ClCO₂ Et (0.1 ml) and DBN (1.0 ml) are added to complete the conversion, and the solution is allowed to stand for 24 hours. Volatile matter is evaporated in vacuo and the viscous residue is purified on a short silica gel column (whose main purpose is to remove the less-mobile DBN) to give an N-blocked pyrrole, which is used for the next step without further purification.

EXAMPLE 5

To a solution of the N-blocked pyrrole of Example 4 (0.635 g, 2.0 mmole) in MeOH (50 ml) is added solid Na₂ CO₃ (0.212 g, 2.0 mmole), and the reaction mixture is stirred at room temperature for 48 hr with separation of the resultant deblocked pyrrole. The mixture is evaporated to dryness, and the residue is triturated thoroughly with H₂ O (25 ml) to dissolve inorganics and extracted with CHCl₃ (3×100 ml). The extract is dried (Na₂ SO₄) and evaporated to give a viscous gum that crystallized upon drying in vacuo for use as an intermediate without further purification. More extensive purification can, however, be effected by using either column chromatography employing silica gel/CHCl₃ or recrystallization from toluene/cyclohexane (1:3).

EXAMPLE 6

Benzoyl isothiocyanate (0.232 g, 1.42 mmole) is added dropwise to a solution of the unblocked pyrrole of Example 5 (0.290 g, 1.18 mmole) in dry CH₂ Cl₂ (100 ml). After 1 h at room temperature, solution is evaporated, and the gummy residue is stirred in Et₂ O/cyclohexane (1:1, 20 ml). The resulting suspension of yellow solid is filtered under N₂ pressure, and the thioureido product is dried in vacuo over P₂ O₅.

EXAMPLE 7

Methyl iodide (0.228 g, 1.61 mmole) is added to a solution of the thioureido product of Example 6 (0.383 g, 0.94 mmole) and DBN (0.140 g, 1.12 mmole) in dry CH₂ Cl₂ (10 ml) at 0° C. The solution is stirred at 0° C. for 15 min., at ambient temperature for 1 h, and then evaporated in vacuo. A solution of the residue in CHCl₃ is chromatographed on a silica gel column with CHCl₃ /methanol (97:3) as eluent to give homogeneous fractions of the methylthio intermediate compound.

EXAMPLE 8

A solution of the methylthio compound of Example 7 (0.358 g, 0.85 mmole) in 100 ml of MeOH that has been saturated with NH₃ at 0° C. is heated at 90°-95° C. for 24 hours in a glass-lined stainless steel bomb. The contents of the chilled bomb are evaporated in vacuo to give a mixture of the desired 2-amino intermediate compound, benzamide, and a by-product that is a 2-methylthio derivative, as opposed to the 2-amino compound. The mixture is dissolved in methanol and the solution is evaporated with silica gel (about 5 g). The mixture is then carefully layered onto the top of a silica-gel chromatography column, which is then eluted with CHCl₃ /MeOH (9:1) to give the methylthio by-product and the desired 2-amino-7-(3-pyridinylmethyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one intermediate. Further purification is obtained by recrystallization from boiling isopropyl acetate in a Soxhlet apparatus.

A solution of the pyridinylmethyl intermediate in 0.lN HCl is hydrogenated with a platinum catalyst at 60 lb/in² H₂ pressure. The catalyst is generated by brief hydrogenation of PtO₂ in 0.lN HCl. When the reaction is complete, the catalyst is removed by filtration under N₂ pressure, and the filtrate is evaporated. A solution of the residue in the minimum amount of ethanol is diluted slowly with a large amount of EtO₂, and the hydrochloride salt is obtained as a white hygroscopic solid of the compound (IC).

EXAMPLE 9

The compound (IC) of Example 8 is tested for enzyme inhibition activity. A purine nucleoside phosphorylase (PNP) enzyme assay is performed in which PNP activity (IC₅₀) for the compound is observed, which is determined radiochemically by measuring the formation of [¹⁴ C]-hypoxanthine from [¹⁴ C]-inosine (see Biomedicine, 33, 39 (1980)) using calf spleen as the enzyme source.

EXAMPLES 10-14

The following compounds of the present invention are prepared that are 2-amino-7-(substituted methyl)-3H,5Hpyrrolo[3,2-d]-pyrimidin-4-ones wherein substituted methyl is --CH₂ R in which the R group is as follows:

Example 10: R=2-methyl-3-piperidinyl

Example 11: R=2-chloro-3-piperidinyl

Example 12: R=2-trifluoromethyl-3-piperidinyl

Example 13: R=2-methoxy-3-piperidinyl

Example 14: R=2-fluoro-3-piperidinyl

The compounds are prepared following the procedures set forth in Examples 1-8 using the appropriate 3-(substituted 3-pyridinyl)-propionitriles as starting materials.

EXAMPLE 15

3-(2-Pyridinyl)propionitrile is prepared in this example using the procedure of V. Boekelheide, et al., J. Am. Chem. Soc., 75, 3243 (1953). A solution of potassium cyanide (83.74 g) in water (160 ml) is added to a solution of freshly distilled 2-vinylpyridine (67.59 g) in acetic anhydrid (131.30 g) with the rate of addition adjusted to maintain gentle refluxing. When the addition is complete, the resulting dark red mixture is heated for about 17 hours at 105° C. in an oil bath with vigorous stirring. The cooled reaction mixture is adjusted to pH 8 with a saturated Na₂ CO₃ solution. The mixture is extracted with CHCl₃ (4×150 ml), washed with water, dried with Na₂ SO₄, and evaporated to a dark viscous oil. The oil is fractionally distilled in vacuo through a Vigreaux column. After a small forerun containing 2-vinylpyridine (0.35 g), the desired 3-(2-pyridinyl)propionitrile is collected as a clear, fluorescent yellow-green, viscous oil: yield 59.8 g; 70.4%; bp 86° C. at 1.0 mm Hg.

EXAMPLES 16-20

The following compounds of the present invention are prepared that are 2-amino-7-(substituted methyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-ones wherein substituted methyl is --CH₂ R in which the R group is as follows:

Example 16: R=2-piperidinyl

Example 17: R=4-piperidinyl

Example 18: R=3-trifluoromethyl-4-piperidinyl

Example 19: R=3-methoxy-2-piperidinyl

Example 20: R=3-fluoro-4-piperidinyl

The compounds are prepared following the procedures set forth in Examples 1-8 and 15 using the appropriate 3-(2- or 4-pyridinyl)-propionitriles as starting materials.

EXAMPLE 21

A pharmaceutical composition for intraperitoneal injection is prepared for testing the compound (IC). An intraperitoneal injection solution containing the compound of Example 8 is dissolved in an aqueous carrier that contains ten percent DMSO.

EXAMPLE 22

The compound (IC) is intraperitoneally injected into Lewis Rats via the test composition of Example 21 to provide 30 mg of the compound (IC), with an injection given twice per day. Controls are used, which receive only the vehicle. At specific times after administration, the animals are sacrificed and plasma samples are prepared. The plasma is extracted with cold 0.5 N HClO₄ and neutralized with solid NH₄ HCO₃. After removal of perchlorate salts, the extract is subjected to HPLC on a reversed phase column (Spherisorb ODSI). A significant increase in plasma inosine is observed in the plasma taken from animals receiving the compound (IC).

EXAMPLES 23-33

Compounds prepared as in Examples 10-20 are each made into a pharmaceutical formulation in accordance with the preparation of Example 21 and the resultant injectable solutions are tested in accordance with the procedure of Example 22. A significant increase in plasma inosine is observed in the plasma taken from animals receiving the compounds of the present invention.

EXAMPLE 34

3-(2-Furanyl)propionitrile is prepared in this example. In a three-neck flask fitted with a condenser and drying tube, magnesium turnings (20 g) are added to a solution of 3-(2-furanyl)acrylonitrile (67.2 g) in dry methanol (2 l). Additional magnesium is added in parts as the reaction rate would allow until a total of 145 g has been added. After about five hours, the solvent is evaporated until the contents set to a solid paste, which is adjusted to a pH of about 6.5 with 6N HCl with cooling. The mixture is extracted with several portions of CHCl₃, dried with Na₂ SO₄, and concentrated to a dark oil. Distillation in vacuo through a short Vigreaux column gives the propionitrile as a colorless oil; yield 49.5 g (72%); bp 46.0°-46.5° C. at 0.5 mm.

EXAMPLE 35

3-(2-Furanyl)propionitrile of Example 34 is further treated in the synthesis of the present invention. Under an atmosphere of dry N₂, the propionitrile (48.7 g), sodium hydride (10.28 g), ethyl formate (32.74 g), and anhydrous tetrahydrofuran (200 ml) are stirred at room temperature with protection from moisture for about 18 hours. The volatile matter is then evaporated, the resulting yellow solid is dissolved in about 20 ml of cold water with ice-bath cooling, and the solution is adjusted to a pH of 6.0 with cold 6N HCl. The resulting heavy oil precipitate is extracted into CHCl₃ , and the extract is washed with water, dried with Na₂ SO₄, and evaporated to give a thin oil which contains the crude formyl compound; yield 53.06 g.

EXAMPLE 36

Glycine methyl ester hydrochloride (67.05 g) and anhydrous sodium acetate (43.79 g) are added to a solution of the crude formyl compound of the previous example (53.05 g) in MeOH/H₂ O (4:1, 1500 ml). After 24 hours, the MeOH is evaporated in vacuo, and the mixture of water and oil is extracted with CHCl₃ . The CHCl₃ layer is dried (Na₂ SO₄) and evaporated to give an amber oil (59.1 g).

EXAMPLE 37

Under a nitrogen atmosphere, ethyl chloroformate (43.68 g) is added dropwise to a solution of the amber oil of Example 36 (59.1 g) and DBN (133 g) in dry CH₂ Cl₂ (400 ml) with external cooling in an ice bath. After stirring at 0° C. for one hour, the solution is allowed to stand at room temperature overnight. After checking progress by TLC, additional ClCO₂ Et and DBN are added to complete the conversion, and the solution is allowed to stand for 24 hours. Volatile matter is evaporated in vacuo, the viscous residue purified on a silica gel column (whose main purpose is to remove the less-mobile DBN) to give an N-blocked pyrrole, a corresponding pyrrole without the ethoxycarbonyl blocking group on the pyrrole nitrogen, and the starting propionitrile.

EXAMPLE 38

To a solution of the N-blocked pyrrole of Example 37 (11.66 g) in MeOH (200 ml) is added solid Na₂ CO₃ (4.23 g), and the reaction mixture is stirred at room temperature for 24 hr with separation of the resultant deblocked pyrrole. The mixture is evaporated to dryness, and the residue is triturated thoroughly with H₂ O (200 ml) to dissolve inorganics and extracted with CHCl₃ (3×200 ml). The extract is dried (Na₂ SO₄) and evaporated to give a viscous gum that crystallized upon drying in vacuo for use as an intermediate without further purification. More extensive purification can, however, be effected by using either column chromatography employing silica gel/CHCl₃ or recrystallization from toluene/cyclohexane (1:3).

EXAMPLE 39

Benzoyl isothiocyanate (4.58 g) is added dropwise to a solution of the unblocked pyrrole of Example 38 (5.15 g) in dry CH₂ Cl₂ (75 ml). After 1 h at room temperature, solution is evaporated, and the gummy residue is dissolved in Et₂ O (100 ml) with almost immediate separation of the crystalline solid, which is collected by filtration. The Et₂ O filtrate is heated to boiling and diluted with an equal volume of warm cyclohexane. On cooling slowly the solution gives additional thioureido product.

EXAMPLE 40

Methyl iodide (8.70 g) is added to a solution of the thioureido product of Example 39 (10.68 g) and DBN (4.15 g) in dry CH₂ Cl₂ (250 ml) at 0° C. The solution is stirred at 0° C. for 15 min., at ambient temperature for 1 h, and then evaporated in vacuo. A solution of the residue in CHCl₃ is chromatographed on a silica gel column with CHCl₃ as eluent to give homogeneous fractions of the methylthio intermediate compound.

EXAMPLE 41

A solution of the methylthio compound of Example 40 (0.80 g, 2.0 mmole) in 25 ml of MeOH that has been saturated with NH₃ at 0° C. is heated at 90°-95° C. for 24 hours in a glass-lined stainless steel bomb. The contents of the chilled bomb are evaporated in vacuo to give a mixture of the 2-amino compound, benzamide and a by-product that is a 2-methylthio derivative, as opposed to the 2-amino compound. The mixture is stirred vigorously for several minutes with 30 ml of 2:1 Et₂ O/cyclohexane, and the insoluble white solid is filtered off and washed with Et₂ O. The filtrate contained most of the benzamide and 2-methylthio components. A solution of the Et₂ O/cyclohexane-insoluble solid (0.425 g) in MeOH is evaporated with appr. 10 g of silica gel. The powdered residue is layered evenly onto the top of a silica gel column, which is then eluted with CHCl₃ /MeOH/HOAc (95:5:1) to give the 2-methylthio by-product and the desired furanyl intermediate. The intermediate is recrystallized by extraction into boiling isopropyl acetate in a Soxhlet apparatus. The white crystals are collected in three crops and dried in vacuo over P₂ O₅ at 110° C. for 7 h.

A solution of the intermediate (116 g, 0.5 mmole) in methanol (50 ml) is hydrogenated with 30% palladium-on-charcoal (40 mg) at 62 lb/in² H₂ pressure for about 36 hours. The catalyst is removed by filtration under N₂ pressure, and the filtrate is evaporated and reevaporated with toluene. The solid residue is recrystallized by extraction into boiling isopropyl acetate in a Soxhlet apparatus. The 2-tetrahydrofuranyl compound (IE) is obtained as a white crystalline solid, which is dried in vacuo over P₂ O₅ at 110° C. for about six hours; yield 73 mg (61.8%); m.p. 284°-286° C. dec.

EXAMPLE 42

The product of Example 41 is tested for enzyme inhibition activity according to the procedure of Example 9, and PNP activity (IC₅₀) for the compound is observed.

EXAMPLE 43

A pharmaceutical composition for intraperitoneal injection is prepared for testing the compound (IE). An intraperitoneal injection solution containing the compound of Example 41 is dissolved in an aqueous carrier that contains ten percent DMSO.

EXAMPLE 44

Using the procedure of Example 16, the compound (IE) is intraperitoneally injected into Lewis Rats via the test composition of Example 43 to provide 30 mg of the compound (IE) and the results are analyzed compared to controls. A significant increase in plasma inosine is observed in the plasma taken from animals receiving the compound (IE).

EXAMPLES 45-49

The following compounds of the present invention are prepared that are 2-amino-7-(substituted methyl)-3H,5Hpyrrolo[3,2-d]pyrimidin-4-ones wherein substituted methyl is --CH₂ --R in which the R group is as follows:

Example 45: R=3-tetrahydrofuranyl

Example 46: R=3-chloro-2-tetrahydrofuranyl

Example 47: R=3-trifluoromethyl-2-tetrahydrofuranyl

Example 48: R=3-methoxy-3-tetrahydrofuranyl

Example 49: R=3-fluoro-2-tetrahydrofuranyl

The compounds are prepared following the procedures set forth in Examples 34-41 using the appropriate 3-(furanyl)-acrylonitriles as starting materials.

EXAMPLE 50

Under a nitrogen atmosphere, a solution of the tetrahydrofuranyl compound (IE) (500 mg) obtained from Example 41 and a crystal of phenol in 2N HBr (20 ml) is stirred for 18 hours at 40° C. The solvent is evaporated in vacuo at low temperature, and the residue is washed with a few ml of Et₂ O by decantation to remove any tribromophenol. A suspension of the residue in H₂ O is adjusted to pH 7 with 1N NaOH to give the bromoalcohol as its free base. The solid is collected, washed with cold water, and dried at room temperature.

A solution of the bromoalcohol in anhydrous dimethylacetamide is chilled in an ice bath and treated with an equimolar portion of PBr₃. The solution is allowed to stir at room temperature for one hour, then the dimethylacetamide is evaporated in vacuo at low temperature using an air pump and dry-ice trap. A suspension of the residue in ice/water is adjusted to pH 7 using 1N NaOH to give the crude reaction product containing the 1,4-dibromo compound. After filtration, washing with cold water, and drying at room temperature, the resulting product is refluxed with sodium sulfide in 50% ethanol/water, or alternatively warmed with Na₂ S in N,N-dimethylacetamide solution; the solvent removed under vacuum, the residue washed with water to remove NaBr, and the pH adjusted to about 7 to precipitate the 2-tetrahydrothienyl compound (IG).

EXAMPLE 51

The compound of Example 50 is tested for enzyme inhibition activity as in Example 9, and PNP activity (IC₅₀) for the compound is observed.

EXAMPLE 52

A pharmaceutical composition for intraperitoneal injection is prepared for testing the compound (IG). An intraperitoneal injection solution is made containing the compound of Example 50 is dissolved in an aqueous carrier that contains ten percent DMSO.

EXAMPLE 53

Using the procedure of Example 16, the compound (IG) is intraperitoneally injected into Lewis Rats via the test composition of Example 52 to provide 30 mg of the compound (IG) and the results are analyzed compared to controls. A significant increase in plasma inosine is observed in the plasma taken from animals receiving the compound (IG).

EXAMPLES 54-58

The following compounds of the present invention are prepared that are 2-amino-7-(substituted methyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-ones wherein substituted methyl is --CH₂ --R in which the R group is as follows:

Example 54: R=3-tetrahydrothienyl

Example 55: R=3-chloro-2-tetrahydrothienyl

Example 56: R=3-trifluoromethyl-2-tetrahydrothienyl

Example 57: R=3-methoxy-2-tetrahydrothienyl

Example 58: R=3-fluoro-2-tetrahydrothienyl

The compounds are prepared following the procedures set forth in Examples 34-41 and 50 using the appropriate 3-(furanyl)-acrylonitriles as starting materials.

EXAMPLE 59

Using the procedure of Example 1, 3-(2-pyrrolyl)propionitrile is prepared using pyrrole-2-carboxaldehyde as the starting material. Following Examples 2-8, the intermediate 2-amino-7-(2-pyrrolylmethyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one is prepared from the propionitrile, from which the 2-pyrrolidinyl compound (II) is obtained by reduction of the intermediate.

EXAMPLE 60

Using the procedure of Example 1, 3-(3-pyrrolyl)propionitrile is prepared using pyrrole-3-carboxaldehyde as the starting material. Following Examples 2-8, the intermediate 2-amino-7-(3-pyrrolylmethyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one is prepared from the propionitrile, from which the 3-pyrrolidinyl compound (IJ) is obtained by reduction of the intermediate.

EXAMPLE 61

Using the procedure of Example 1, 3-(2-pyranyl)propionitrile is prepared using 2-pyrancarboxaldehyde as the starting material. Following Examples 2-8, the intermediate 2-amino-7-(2-pyranylmethyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one is prepared from the propionitrile, from which the 2-tetrahydropyranyl compound (IL) is obtained by reduction of the intermediate.

EXAMPLE 62

Using the procedure of Example 1, 3-(3-pyranyl)propionitrile is prepared using 3-pyrancarboxaldehyde as the starting material. Following Examples 2-8, the intermediate 2-amino-7-(3-pyranylmethyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one is prepared from the propionitrile, from which the 3-tetrahydropyranyl compound (IM) is obtained by reduction of the intermediate.

EXAMPLE 63

Using the procedure of Example 1, 3-(4-pyranyl)propionitrile is prepared using 4-pyrancarboxaldehyde as the starting material. Following Examples 2-8, the intermediate 2-amino-7-(4-pyranylmethyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one is prepared from the propionitrile, from which the 4-tetrahydropyranyl compound (IN) is obtained by reduction of the intermediate. 

What is claimed is:
 1. A compound of the formula 2-amino-7-(substituted methyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one wherein substituted methyl is --CH₂ --R wherein R is optionally substituted by halogen, hydroxy, alkoxy, alkyl or trifluoromethyl.
 2. The compound of claim 1 wherein the heteroalicyclic group is 2-, 3-, or 4-piperidinyl.
 3. The compound of claim 1 wherein the heteroalicyclic group is 2- or 3-tetrahydrofuranyl.
 4. The compound of claim 1 wherein the heteroalicyclic group is 2- or 3-tetrahydrothienyl.
 5. The compound of claim 1 wherein the heteroalicyclic group is 2- or 3-pyrrolidinyl.
 6. The compound of claim 1 wherein the heteroalicyclic group is 2-, 3-, or 4-tetrahydropyranyl.
 7. The compound of claim 1 wherein R has one or two substituents selected from the group consisting of chloro, fluoro, methoxy, ethoxy, propoxy, butoxy, methyl, ethyl, propyl and butyl.
 8. A method for the selective suppression of mammalian T-cell function without diminished effect on humoral immunity which comprises administering to a mammal the compound of claim 1, whereby said compound inhibits purine nucleoside phosphorylase and thereby T-cell formation.
 9. A method for the selective suppression of mammalian T-cell function without diminished effect on humoral immunity which comprises administering to a mammal the compound of claim 2, whereby said compound inhibits purine nucleoside phosphorylase and thereby T-cell formation.
 10. A method for the selective suppression of mammalian T-cell function without diminished effect on humoral immunity which comprises administering to a mammal the compound of claim 3, whereby said compound inhibits purine nucleoside phosphorylase and thereby T-cell formation.
 11. A method for the selective suppression of mammalian T-cell function without diminished effect on humoral immunity which comprises administering to a mammal the compound of claim 4, whereby said compound inhibits purine nucleoside phosphorylase and thereby T-cell formation.
 12. A method for the selective suppression of mammalian T-cell function without diminished effect on humoral immunity which comprises administering to a mammal the compound of claim 5, whereby said compound inhibits purine nucleoside phosphorylase and thereby T-cell formation.
 13. A method for the selective suppression of mammalian T-cell function without diminished effect on humoral immunity which comprises administering to a mammal the compound of claim 6, whereby said compound inhibits purine nucleoside phosphorylase and thereby T-cell formation.
 14. A pharmaceutical composition for the selective suppression of mammalian T-cell function without diminished effect on humoral immunity which comprises an effective amount of the compound of claim 1 capable of said selective suppression and a pharmaceutically acceptable carrier or diluent therefor.
 15. A pharmaceutical composition for the selective suppression of mammalian T-cell function without diminished effect on humoral immunity which comprises an effective amount of the compound of claim 2 capable of said selective suppression and a pharmaceutically acceptable carrier or diluent therefor.
 16. A pharmaceutical composition for the selective suppression of mammalian T-cell function without diminished effect on humoral immunity which comprises an effective amount of the compound of claim 3 capable of said selective suppression and a pharmaceutically acceptable carrier or diluent therefor.
 17. A pharmaceutical composition for the selective suppression of mammalian T-cell function without diminished effect on humoral immunity which comprises an effective amount of the compound of claim 4 capable of said selective suppression and a pharmaceutically acceptable carrier or diluent therefor.
 18. A pharmaceutical composition for the selective suppression of mammalian T-cell function without diminished effect on humoral immunity which comprises an effective amount of the compound of claim 5 capable of said selective suppression and a pharmaceutically acceptable carrier or diluent therefor.
 19. A pharmaceutical composition for the selective suppression of mammalian T-cell function without diminished effect on humoral immunity which comprises an effective amount of the compound of claim 6 capable of said selective suppression and a pharmaceutically acceptable carrier or diluent therefor. 